AIM: The EUCCLID study aims to compare the quality of type 2 diabetes (DM2) care and the prevalence of complications in primary care DM2 patients in Europe. DESIGN: A cross-sectional survey consisting of three parallel studies: (1) study on actual clinical practice; (2) study on patient's perspective of diabetes care; (3) study on general practitioner's perspective of diabetes care. METHODS: Patients will be randomly selected from a list of all patients known to the participating GPs with DM2 for whom the GP is the main diabetes care provider. Exclusion criteria will include people with type 1 diabetes mellitus, diabetes of pregnancy, serious mental illness, unable to complete a questionnaire in national language or unable to give written informed consent. Approximately 12,000 patients will be included. Participants will have a detailed medical history and anthropometric measurements, blood and urine will be collected and questionnaires will be taken. Endpoints will include quality indicators of clinical DM2 care, prevalence of diabetic complications, knowledge, attitudes, barriers and behaviour affecting good control in DM2 patients, quality of life and patients' satisfaction with diabetes care. We will also determine primary care physician's attitudes, behaviour and perception of barriers to deliver effective diabetes care.